N-doping enriched porous MgO-modified biochar enables efficient anionic acid fuchsin dye removal

Developing efficient biochar (BC) adsorbent for pollution removal has been a long-term exploration. However, the negative charge surface of pristine BC seriously impedes the transfer of anionic dye through the pore of BC and results in low adsorption capacity. Herein, N-doping enriched porous MgO-modified biochar (MBC) was successfully prepared through a facile nitrate activation method for anionic acid fuchsin (AF) removal. The N-doped group of secondary amine in MBC changes the surface charge of BC and facilitate the AF adsorption onto MgO. The as-prepared MBC exhibited superior adsorption capacity of 328 mg⋅g−1. The adsorption process was well aligned with the Freundlich and pseudo-second-order kinetics models indicating a hybrid physicochemical adsorption mechanism. Further mechanism investigation indicates that N-doped group, MgO and functional groups in biochar matrix primarily contribute to AF adsorption. The mechanism includes: electrostatic attraction, π-π interaction, hydrogen bonding and pore filling. This research provides an environmentally friendly nitrate activation strategy for BC, which overcomes the inherent defects of BC in negative charge surface and provides a facile way of biomass valorization for pollution removal from the aquatic environment.